Continuous versus bolus norepinephrine administration to treat hypotension after induction of general anaesthesia in low-to-moderate risk noncardiac surgery patients: a randomised trial.

Background: Hypotension after induction of general anaesthesia (postinduction hypotension) is common in patients undergoing noncardiac surgery and frequently requires treatment with vasopressors such as norepinephrine. We tested the hypothesis that giving norepinephrine continuously using a syringe infusion pump, compared with giving it as repeated manual boluses, reduces postinduction hypotension within 15 min after starting induction of general anaesthesia in low-to-moderate risk noncardiac surgery patients.

Methods: Patients undergoing elective noncardiac surgery were randomised to either continuous norepinephrine infusion or manual bolus norepinephrine administration intravenously during induction of general anaesthesia. In both groups, norepinephrine was administered through a peripheral venous catheter. Blood pressure was measured by clinicians using intermittent oscillometry. We additionally performed blinded continuous noninvasive blood pressure monitoring to quantify the duration and extent of postinduction hypotension. The primary endpoint was postinduction hypotension, defined as the area under a MAP of 65 mm Hg within 15 min after starting induction of general anaesthesia.

Results: From 276 randomised patients, 261 had complete data (median age: 62 yr; 40% female). The median (25th-75th percentile) area under a MAP of 65 mm Hg was 3.6 (0.0-16.6) mm Hg × min in patients assigned to continuous norepinephrine infusion, compared with 5.5 (0.5-24.5) mm Hg × min in patients assigned to manual bolus norepinephrine administration (P=0.070). The median duration of MAP values <65 mm Hg was 1.0 (0.0-2.5) min vs 1.4 (0.2-3.2) min (P=0.052).

Conclusions: Continuous administration of norepinephrine, compared with repeated manual bolus doses, did not reduce postinduction hypotension in low-to-moderate risk noncardiac surgery patients who had intermittent oscillometric blood pressure monitoring.